FILE- In this Dec. 26, 2015, file photo, Philadelphia Eagles head coach Chip Kelly watches from the sidelines before an NFL football game against the Washington Redskins in Philadelphia. Michael PerezAP

FILE- In this Dec. 26, 2015, file photo, Philadelphia Eagles head coach Chip Kelly watches from the sidelines before an NFL football game against the Washington Redskins in Philadelphia. Michael PerezAP

Breathless anticipation: 49ers hire Chip Kelly as next head coach

Put on your track shoes and make sure you’re well hydrated: The 49ers on Thursday hired Chip Kelly, the controversial and mostly successful architect of football’s fastest-paced offenses, as their next head coach.

The announcement was made via Twitter by team CEO Jed York, who along with general manager Trent Balke, met with Kelly last week in New York. Kelly, 52, was fired 15 games into Philadelphia’s 7-9 season but put together back-to-back 10-6 campaigns before that.

Most teams hold an introductory press conference with their new head coach soon after the hire is announced. The 49ers don’t plan on a press conference until mid week next week as Kelly builds his new staff, a team spokesman said.

Prior to joining the NFL, Kelly flourished at the University of New Hampshire and the University of Oregon and his teams always have been known for high-powered, fast-paced offenses, something the 49ers are intent on improving after finishing 31st in the league in 2015.

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“Guess I might have to start running right now to get in shape,” 49ers receiver Torry Smith wrote on Twitter after the announcement was made.

Kelly’s Eagles offenses finished ranked in the Top 5 in 2013 and 2014 before slipping to 12th this past season. His defenses, however, finished 29th, 28th and 30th over the past three years with some players complaining that the pace of Kelly’s offense meant they were on the field too much. The Eagles had the worst time of possession in the NFL in 2015; the 49ers finished second-worst in that category.

“I feel bad for (defensive coordinator) Billy (Davis) because our numbers are so skewed," pass rusher Connor Barwin told reporters in Philadelphia last week. "We played three more games than Seattle. I'm not trying to make excuses, but we weren't as bad as some of the numbers look. That's because we play three more games than other teams. That makes a difference."

Other players complained that Kelly worked them too hard and was so accustomed to college players he didn’t know how to deal with professional athletes. That also was a complaint some players had of Jim Harbaugh after he and the 49ers parted ways following the 2014 season.

The 49ers spoke to at least one player, defensive end Arik Armstead, about potentially hiring Kelly. Armstead played for Kelly at the University of Oregon and told team officials he thought his teammates would be able to play for Kelly, according to a league source.

Tom Gamble, the 49ers’ senior personnel executive, was part of the Eagles’ front office in 2013-14 and the two have a good relationship. Gamble is believed to have encouraged the initial interview and assured 49ers officials that they would be able to work with Kelly.

Kelly won a power struggle in the Eagles’ front office last year, one that landed him the additional title of head of football operations. But he was criticized for subsequent personnel moves, such as trading All-Pro running back LeSean McCoy to the Bills and dealing quarterback Nick Foles for Sam Bradford. Bradford finished the season ranked 26th in passer rating, one spot ahead of Blaine Gabbert.

Baalke is expected to maintain personnel control with the 49ers.

Kelly, meanwhile, is thought to be fond of quarterback Colin Kaepernick, who was benched after eight games in 2015 and who is due to earn a base salary of nearly $12 million in the upcoming season. Kaepernick’s status for next season is in limbo although team officials have said repeatedly that speculation that he will be cut or traded is premature.

Kelly will be filling out his staff in coming days. One name that has been mentioned as a potential offensive coordinator is Ryan Day, his quarterbacks coach in Philadelphia who obviously is familiar with Kelly’s offense. Davis, the Eagles’ defensive coordinator, had the same job under Mike Nolan in 2005.